Degradable bio-based polyurethane wood protective coating as well as preparation method and application thereof

Abstract

The invention discloses a degradable bio-based polyurethane wood protective coating. The coating comprises the following components: 40-60 parts of modified bio-based polyester polyol, 10-20 parts of a cross-linking agent, 3-8 parts of an antibacterial agent, 1-3 parts of a weather-resistant agent, 2-5 parts of a hydrolysis stabilizer, 20-30 parts of a solvent, 1-3 parts of a coupling agent, 0.5-1.5 parts of a leveling agent and 0.5-1.5 parts of a defoaming agent. The preparation method of the degradable bio-based polyurethane wood protective coating comprises the following steps: firstly, esterifying binary acid, dihydric alcohol and renewable biomass resources to prepare bio-based polyester polyol, then modifying the bio-based polyester polyol by using a hydrophobic modifier, finally mixing and dispersing the bio-based polyester polyol with other auxiliaries uniformly, and curing to obtain the degradable bio-based polyurethane wood protective coating. The coating has a static water contact angle of 113 degrees at most after being coated, the QUV aging life reaches 480 h, the antibacterial rate reaches 90% at most, the 90-day compost degradation weight loss rate reaches 60% at most, and the coating is environmentally friendly, low in VOC emission and suitable for efficient and durable protection of wood. The invention also provides an application of the degradable bio-based polyurethane wood protective coating.

Description

Technical Field

[0001] This invention relates to the field of wood protective materials technology, specifically to a biodegradable bio-based polyurethane wood protective coating, its preparation method, and its application. Background Technology

[0002] Wood, as a natural, renewable, and biodegradable green material, is widely used in construction, furniture, and interior decoration. However, its porous structure and hydrophilicity make it susceptible to moisture penetration, ultraviolet radiation, fungal attack, and insect infestation, leading to cracking, deformation, decay, and color aging, severely shortening its lifespan. To protect wood, protective coatings are usually applied to its surface. Currently, widely used traditional wood coatings are mainly based on petroleum-derived polymer resins, such as polyurethane and acrylates. While these coatings provide a certain physical barrier, they have inherent drawbacks such as being non-renewable, having poor biodegradability, high VOC (volatile organic compound) emissions, and a significant environmental impact.

[0003] With increasing environmental awareness, bio-based polymers have attracted widespread attention due to their renewable and environmentally friendly properties. Existing technologies have explored the application of some bio-based polymers in wood, for example: Xie Chengxin et al. introduced the bio-based molecule sorbitan monooleate (SP) as a bifunctional crosslinking agent to enhance the mechanical and hydrophobic properties of waterborne polyurethane (WPU) wood adhesives. Through the synergistic effect of multiple hydroxyl groups and long hydrophobic oleic acid chains, a three-dimensional network was constructed within the WPU, verifying that bio-based molecules with designed functions can enhance the mechanical and hydrophobic properties of polymer networks, providing a scalable green strategy for producing sustainable materials that meet performance requirements. (Sustain. Mater. Technol, 46, 2025, e01669) However, such methods face high costs and difficulties in process control during actual production.

[0004] Cao Mengting et al. from Fujian Agriculture and Forestry University prepared hydrophobic, weather-resistant, and transparent silicone resin coatings on wood surfaces using a simple impregnation method with polymethylhydrosiloxane (PMHS) and 2,4,6,8-tetramethyl-2,4,6,8-tetravinylsiloxane (V4) as reactants. The results showed that after modification with PMHS / V4 silicone resin, the wood surface was grafted with hydrophobic long chains and groups, significantly increasing the contact angle to 131.1°, exhibiting excellent hydrophobicity. Furthermore, the water absorption rate of the modified wood decreased from 108.5% to 31.3%. (Chemical Research and Application, 34(05), 2022, 1156-1163) However, the interfacial bonding strength between the coating formed by this physical coating method and the wood matrix may be insufficient, affecting its durability.

[0005] Gengen Chemical Industries, Ltd. of Japan, in collaboration with the Forest Research and Development Institute (FFPRI), has developed a cellulose nanofiber (CNF) using a unique enzyme / wet pulverization method. Based on this CNF, they have developed a wood primer with long-lasting protective properties. This CNF wood primer forms a unique film on the wood surface, improving the adhesion between the wood and the coating, inhibiting UV transmission, thereby reducing discoloration of the wood substrate by more than half, and significantly suppressing surface cracking, peeling, and other defects in the coating. (CNF coating formulation technology established, applicable to outdoor wood coatings, EB / OL, CoatingMedia, 2020 / 07 / 31) However, the aforementioned existing technologies either rely on physical coating, resulting in insufficient interfacial adhesion, or use non-bio-based siloxane materials, making it difficult to balance environmental friendliness and long-term durability. Therefore, there is an urgent need in the field to develop a biodegradable bio-based polyurethane protective coating with excellent overall performance. Summary of the Invention

[0006] The purpose of this invention is to provide a biodegradable bio-based polyurethane wood protective coating. Starting from renewable biomass resources, an environmentally friendly and biodegradable bio-based polyester polyol is prepared. Furthermore, the bio-based polyester polyol is hydrophobically modified, and silane-modified graphene oxide is added to enhance the coating's hydrophobicity and weather resistance. Further, by loading nano-zinc oxide onto the surface of fumed nano-silica and modifying it with silane, an antibacterial agent with good dispersibility and antibacterial properties is obtained. This agent can undergo a dehydration condensation reaction with the bio-based polyester polyol, solving the problem of long-lasting antibacterial effect.

[0007] To solve this technical problem, the present invention adopts the following technical solution: A biodegradable bio-based polyurethane wood protective coating, comprising the following components by weight: Modified bio-based polyester polyol: 40-60 parts; Crosslinking agent: 10-20 parts; Antibacterial agent: 3-8 parts; Weather resistant agent: 1-3 parts; Hydrolysis stabilizer: 2-5 parts; Solvent: 20-30 parts; Coupling agent: 1-3 parts; Leveling agent: 0.5-1.5 parts; Defoamer: 0.5-1.5 parts.

[0008] Furthermore, the modified bio-based polyester polyol is obtained by modifying polyester polyols prepared from renewable biomass resources, diacids, and diols. The renewable biomass resource is at least one of castor oil, soybean oil, and rice husk alcohol; the dicarboxylic acid is at least one of adipic acid, succinic acid, and sebacic acid; and the diol is at least one of 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol. The modification involves using at least one of lauric anhydride, palmitic anhydride, glycidyl palmitate, and glycidyl stearate to hydrophobically modify the bio-based polyester polyol.

[0009] Furthermore, the antibacterial agent is modified nano-zinc oxide supported porous silica, and its preparation method includes the following steps: P1. Add porous silica with a particle size of 1-5 μm to a 70% ethanol-water solution at a mass ratio of 1:(0.06-0.12), and sonicate for 10-30 min to hydrolyze. Then add zinc nitrate to the ethanol-water solution at a mass ratio of 1:(0.1-0.16), and stir at 200-600 rpm for 10-30 min until homogeneous to obtain the pre-dispersion. P2. Add 2 mol / L sodium hydroxide solution to the pre-dispersion obtained in step P1 until the pH is 11-12 to precipitate zinc hydroxide. After precipitation, centrifuge to collect the solid, wash with deionized water and ethanol, and dry at 80-100℃ for 12-24 h. Then calcine in a muffle furnace at 500-600℃ for 4-6 h and cool to obtain nano-zinc oxide supported porous silica. P3. Add KH550 silane coupling agent to a 95% ethanol-water solution at a volume ratio of 1:(0.03-0.07), stir at 200-600 rpm for 5-15 min, and sonicate for 20-40 min to fully hydrolyze. Then, add the nano-zinc oxide-supported porous silica obtained in step P2 to the hydrolysate at a ratio of 0.05-0.2 g / ml. Stir at 40-60 ℃ for 4-6 h, centrifuge, wash with deionized water and ethanol, and dry at 80-100 ℃ for 5-8 h to obtain modified nano-zinc oxide-supported porous silica.

[0010] Furthermore, the weather-resistant agent is at least one of graphene, graphene oxide, and silane-modified graphene oxide; The crosslinking agent is at least one of hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and trimers or biuret derivatives of the above substances. The hydrolysis stabilizer is at least one of Lanxess Stabaxol I, Lanxess Stabaxol P200, Lanxess Stabaxol P100, and BASF Irganox GX-2411; The solvent is at least one of butyl acetate (BAC), propylene glycol methyl ether acetate (PGMEA), and dimethyl carbonate (DMC); The coupling agent is at least one of γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), and γ-methacryloyloxypropyltrimethoxysilane (KH-570); The leveling agent is a polyether-modified polydimethylsiloxane leveling agent; the defoamer is a polysiloxane-polyether copolymer defoamer.

[0011] Another object of the present invention is to provide a method for preparing a biodegradable bio-based polyurethane wood protective coating, comprising the following steps: S1. Preparation and modification of bio-based polyester polyols: S11. Esterification reaction: In a reactor equipped with a water separator, condenser and stirring device, add diacid, diol and renewable biomass resources at a mass ratio of 1:(0.3-0.6):(0.1-0.5). Under nitrogen protection, slowly raise the temperature to 180-220℃ at a heating rate of 2-3℃ / min and carry out esterification and dehydration reaction for 4-6 h until a bio-based polyester polyol with the required hydroxyl value and acid value is obtained. S12. Hydrophobic modification: The bio-based polyester polyol obtained in step S11 and the hydrophobic modifier are added to a beaker at a mass ratio of 1:(0.08-0.12). The mixture is stirred at 120-140℃ for 2-4 h. Long-chain alkyl groups are grafted onto the polyol molecular chain through alcoholysis esterification reaction to obtain hydrophobically modified bio-based polyester polyol. S2. Preparation of premixed slurry: The bio-based polyester polyol, solvent, antibacterial agent, weathering agent, hydrolysis stabilizer and coupling agent obtained in step S1 are added to a high-speed disperser in proportion and dispersed at a speed of 1000-1500 rpm for 30-45 min to obtain a uniform premixed slurry. S3. Coating preparation: Add crosslinking agent, leveling agent and defoamer to the premixed slurry obtained in step S2 in proportion, and continue to disperse at a speed of 500-800 rpm for 10-15 min to make it evenly mixed, thus obtaining the biodegradable bio-based polyurethane wood protective coating.

[0012] Another objective of this invention is to provide an application of a biodegradable bio-based polyurethane wood protective coating, which is applied to the wood surface to form a protective coating. The prepared bio-based polyurethane wood protective coating is applied to the wood surface using different application methods. The coating parameters are appropriately adjusted according to the different application methods to achieve optimal hydrophobicity and antibacterial properties on the wood surface. The coating methods include brushing, roller coating, spraying, or vacuum pressure impregnation. In particular, when using the vacuum pressure impregnation process, it is recommended to dilute the composition with a suitable solvent to a solid content of 30%-40%, and impregnate it at 50-60°C and 0.5-0.8 MPa for 30-60 minutes. This allows the hydrophobic modifier, antibacterial agent, and other functional components to penetrate into the wood to a depth of 1-2 mm, achieving synergistic protection both inside and out.

[0013] By adopting the above technical solution, the beneficial effects of the present invention are as follows: 1. Firstly, the biodegradable bio-based polyurethane wood protective coating prepared by this invention contains over 50% bio-based raw materials (based on polyol solids), significantly reducing reliance on traditional fossil resources and providing an environmentally friendly, non-toxic, and sustainable wood protective coating solution. Testing showed that the VOC content of the coating was less than 50 g / L after 48 hours of drying and less than 30 g / L after 28 days of drying. Secondly, this invention utilizes 1,2-propanediol to attack and open the triglyceride structure in castor oil, resulting in alcoholysis to obtain monoglycerides, diglycerides, and ricinoleic acid. The hydroxyl groups (-OH) of the castor oil alcoholysis products, the carboxyl groups (-COOH) of adipic acid, and the hydroxyl groups (-OH) of 1,2-propanediol undergo dehydration esterification to prepare a bio-based polyester polyol. Subsequently, the prepared bio-based polyester polyol is mixed with glycidyl palmitate or other hydrophobic monomers, causing the epoxy groups to open and form new hydroxyl groups. These hydroxyl groups are then linked to the bio-based polyester polyol via ether bonds, allowing the bio-based polyester polyol to connect with the long-chain hydrophobic monomers through ring-opening esterification. This imparts excellent hydrophobicity to the bio-based polyester polyol, with a static contact angle of 110°-115° as tested. Finally, using the bio-based polyester polyol as the main component of a wood protective coating, this coating can undergo controlled degradation under certain conditions after its service life, without causing environmental pollution, aligning with the development direction of green chemistry.

[0014] 2. First, by combining bio-based polyester polyol with graphene-based weathering agent, good hydrophobicity is provided. The bio-based polyester polyol provides good hydrophobicity through the long alkyl chains grafted on the main chain, while the graphene-based weathering agent provides good physical barrier and water repellency. Furthermore, the amino-NH2 of silane-modified graphene oxide and the residual carboxyl-COOH of bio-based polyester polyol form stable amide bonds -NH-CO- through a dehydration condensation reaction such as -NH2 + -COOH → -NH-CO- + H2O, or, with the participation of isocyanate group -NCO, undergo a nucleophilic addition reaction such as -NH2 + -NCO → -NHCONH- to generate urea bonds -NHCONH- and be attached to the main chain. The synergy between these factors results in better overall consistency and good waterproof performance after the coating dries, with the water absorption rate of wood decreasing by 30%-50% after 24 hours of application. Secondly, by introducing silane-modified graphene oxide, the coating acquires excellent physical shielding and UV absorption capabilities. QUV accelerated aging tests show that the aging life of wood protected by this coating is extended to 400-500 hours, more than twice that of traditional petroleum-based coatings (150-200 hours). Finally, nano-zinc oxide is deposited on the surface of porous silica using a chemical precipitation method, and its dispersion in the coating is improved using a silane coupling agent. The prepared nano-zinc oxide-supported porous silica imparts excellent antibacterial and antifungal properties to the coating, exhibiting good dispersibility, long-lasting effect, and an inhibition rate of over 90% against common wood-decaying fungi such as Aspergillus niger and Penicillium.

[0015] 3. By introducing a carbodiimide-based hydrolysis stabilizer into the coating, it can actively capture the carboxylic acid produced by hydrolysis, terminating the autocatalytic reaction. After 168 hours of testing at 85℃ / 85% relative humidity, the coating remained intact, without blistering, cracking, or chalking, while the control sample showed severe failure. Furthermore, the preparation process of this composite coating is simple, with mild reaction conditions, making it suitable for industrial production. Utilizing agricultural waste materials such as rice husk furfuryl alcohol as the starting point for preparing bio-based polyester polyols effectively controls costs and reduces environmental pollution. The final product cost is only 10%-15% higher than pure petroleum-based coatings, offering extremely high cost-effectiveness. Attached Figure Description

[0016] To illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0017] Figure 1 Images of the various embodiments and comparative samples of the present invention after being coated and subjected to a damp heat stability test.

[0018] in Figure 1Figure a is an image of Example 1, Figure b is an image of Example 2, Figure c is an image of Example 3, Figure d is an image of Comparative Example 1, Figure e is an image of Comparative Example 2, and Figure f is an image of Comparative Example 3. Detailed Implementation

[0019] To further explain the technical solution of the present invention, specific embodiments are described in detail below, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the reagents, equipment, and methods used in the present invention are commercially available reagents, equipment, and methods conventionally used in this technical field.

[0020] Example 1

[0021] This embodiment discloses a biodegradable bio-based polyurethane wood protective coating, which comprises the following components by weight: Bio-based polyester polyols: 60 parts; Crosslinking agent: 15 parts; Antibacterial agent: 5 parts; Weather resistant agent: 2 parts; Hydrolysis stabilizer: 3 parts; Solvent: 25 parts; Coupling agent: 2 parts; Leveling agent: 0.5 parts; Defoamer: 0.5 parts.

[0022] Furthermore, a method for preparing a biodegradable bio-based polyurethane wood protective coating includes the following steps: (1) Preparation of bio-based polyester polyol: Weigh and add 100 parts of adipic acid, 50 parts of 1,2-propanediol and 30 parts of castor oil to the reaction vessel by weight, purge with nitrogen, slowly heat to 200℃ at a rate of 3℃ / min, stir and react for 5 h, remove the generated water through a water separator, and stop the reaction when the acid value drops to below 3 mg KOH / g to obtain a bio-based polyester polyol with a hydroxyl value of 120 mg KOH / g.

[0023] (2) Hydrophobic modification: 10 parts of glycidyl palmitate were added to 100 parts of bio-based polyester polyol obtained in step (1) by weight, and the reaction was carried out at 130 °C and stirred for 3 h to obtain hydrophobic modified bio-based polyester polyol.

[0024] (3) Preparation of modified nano-zinc oxide supported porous silica: Weigh 15 g of porous silica (particle size 1-5 μm) and ultrasonically disperse it in 150 ml of 70% ethanol aqueous solution, then add 20 g of zinc nitrate and stir to dissolve; A 2 mol / L NaOH solution was added dropwise to the solution until the pH reached 11, which generated zinc hydroxide precipitate. After precipitation, the solution was centrifuged, washed with deionized water and ethanol, dried at 80°C for 16 h, and then calcined at 500°C for 5 h in a muffle furnace. After cooling, nano-zinc oxide supported porous silica was obtained. Add 5 ml of KH550 silane coupling agent to 200 ml of 70% ethanol aqueous solution, stir at 400 rpm for 10 min, and sonicate for 30 min to hydrolyze. Add 20 g of the above-mentioned nano-zinc oxide supported porous silica, stir at 50℃ for 4 h, centrifuge, wash with deionized water and ethanol, and dry at 80℃ for 6 h to obtain modified nano-zinc oxide supported porous silica.

[0025] (4) Coating preparation: Weigh 60 parts of the modified polyester polyol obtained in step (2) according to the proportion, and add it together with 25 parts of solvent butyl acetate, 2 parts of weather-resistant agent silane-modified graphene oxide, 5 parts of antibacterial agent modified nano zinc oxide supported porous silica, 3 parts of hydrolytic stabilizer (Stabaxol P100), and 2 parts of coupling agent KH550 into a dispersion vessel, and disperse at high speed at 1200 rpm for 40 min. Then add 15 parts of crosslinking agent (HDI trimer), 0.5 parts of leveling agent (BYK-333), and 0.5 parts of defoamer (BYK-024), and disperse at 600 rpm for 12 min to obtain the biodegradable bio-based polyurethane wood protective coating.

[0026] Example 2

[0027] This embodiment discloses a biodegradable bio-based polyurethane wood protective coating with the same components as in Example 1, but without hydrophobic modification of the bio-based polyester polyol, in order to compare the hydrophobic modification effect.

[0028] Furthermore, a method for preparing a biodegradable bio-based polyurethane wood protective coating omits step (2) hydrophobic modification step compared to the preparation method in Example 1, while the remaining steps are the same as in Example 1.

[0029] Example 3

[0030] This embodiment discloses a biodegradable bio-based polyurethane wood protective coating with the same components as in Example 1, but replacing 5 parts of modified nano zinc oxide-supported porous silica antibacterial agent in Example 1 with 5 parts of tea tree oil to compare the antibacterial effect.

[0031] This embodiment also discloses a method for preparing a biodegradable bio-based polyurethane wood protective coating. Compared with Example 1, step (3) of preparing modified nano zinc oxide-supported porous silica is omitted, and the remaining steps are the same as in Example 1.

[0032] Comparative Example 1

[0033] This comparative example refers to the physical coating method for hydrophobic coating mentioned in the paper "Preparation of PMHS / V4 Organosilicon Resin Hydrophobic Coating on Wood Surface" published by Cao Mengting et al. of Fujian Agriculture and Forestry University in the background art. A 5% concentration of PMHS / V4 modified liquid was used to immerse the same batch of pine wood specimens for 5 min to prepare the hydrophobic coating.

[0034] Comparative Example 2

[0035] This comparative example discloses a biodegradable bio-based polyurethane wood protective coating, which, compared to Example 1, adds 5 parts of organosilicon hydrophobic agent but does not modify the bio-based polyester polyol for hydrophobicity, and compares the hydrophobic effects.

[0036] This comparative example discloses a method for preparing a biodegradable bio-based polyurethane wood protective coating. Compared with the preparation method of Example 1, step (2) hydrophobic modification step is omitted, and the remaining steps are the same as in Example 1.

[0037] Comparative Example 3

[0038] This comparative example discloses a biodegradable bio-based polyurethane wood protective coating with the same composition as Example 1, but replacing 5 parts of modified nano-zinc oxide-supported porous silica antibacterial agent in Example 1 with 5 parts of nano-zinc oxide-supported porous silica antibacterial agent, without silane coupling modification.

[0039] This comparative example also discloses a method for preparing a biodegradable bio-based polyurethane wood protective coating. Except for step (3), which omits the final KH550 modification step, the other steps are the same as the preparation method in Example 1.

[0040] like Figure 1 The images shown are of samples from various embodiments and comparative examples of the present invention after applying the coatings and undergoing hygrothermal stability testing. It can be seen that Examples 1 and 3 showed only very slight loss of gloss, with virtually no abnormal changes. Example 2 showed slight shrinkage and discoloration, while Comparative Examples 1 and 2 showed relatively severe blistering, peeling, and chalking. Comparative Example 3 showed only slight blistering and loss of gloss. The accompanying drawings demonstrate that the biodegradable bio-based polyurethane wood protective coating prepared by the present invention has good coating performance and good aging resistance.

[0041] All embodiments and comparative examples of the present invention were subjected to performance tests. The contact angle was tested according to ASTM D5946, the water absorption rate according to ASTM D570, the QUV aging life according to ASTM G154, the antibacterial property according to ASTM D5590, the VOC content test according to GB 18581-2022, the wet heat stability test was conducted at a temperature of 85 ℃ and a humidity of 85%, and the degradation weight loss rate was tested in a 90-day composting test. The specific test results are shown in Table 1.

[0042] Table 1. Test results of film performance obtained in Examples 1 to 3 and Comparative Examples 1 to 3

[0043] As shown in Table 1, the performance test data indicates that Example 1 exhibits the best overall performance. By hydrophobically modifying the bio-based polyester polyol, it acquires excellent hydrophobic properties. Furthermore, the addition of silane-modified graphene oxide weathering agent enhances the overall hydrophobicity of the coating. In addition, the addition of modified nano-zinc oxide-supported porous silica antibacterial agent effectively improves the overall antibacterial properties of the coating. Moreover, the surface amino groups of the modified nano-zinc oxide-supported porous silica react with the residual carboxyl groups of the bio-based polyester polyol or with isocyanate groups to form stable chemical bonds, helping to form a denser coating structure and prolonging the antibacterial durability.

[0044] Comparing Examples 1 and 2, it was found that without hydrophobic modification of the bio-based polyester polyol, the contact angle and weather resistance of the coating decreased significantly, indicating the necessity of hydrophobic modification through chemical methods. Comparing Examples 1 and 3, it was found that if the antibacterial agent was changed to tea tree oil, the antibacterial activity of the coating decreased from 90% to 83%, indicating that the modified nano-zinc oxide-supported porous silica has superior antibacterial properties.

[0045] Comparing Example 1 and Comparative Example 1, it was found that although the coating prepared in Comparative Example 1 exhibited excellent hydrophobicity in the initial stage, its interfacial adhesion, stability, and weather resistance were poor. Bubbling and peeling occurred as testing progressed. Furthermore, Comparative Example 1 had a high water absorption rate and virtually no antibacterial ability. The coating prepared in Example 1, however, showed better overall performance after application. Comparative Examples 1 and 2 also revealed that, compared to the method of hydrophobic modification of bio-based polyester polyols, coatings prepared by directly adding hydrophobic agents showed a certain degree of improvement in both hydrophobicity and weather resistance. The dispersibility was reduced, and slight powdering occurred during the test, proving that the method of hydrophobic modification of bio-based polyester polyols in this invention is more advantageous than directly adding hydrophobic agents. Comparing Example 1 and Comparative Example 3, it was found that if the nano-zinc oxide-supported porous silica is not modified with silane, its dispersibility is greatly reduced, resulting in a decrease in its binding ability with bio-based polyester polyols, causing a decrease in the overall performance of antibacterial and hydrophobic properties. Furthermore, slight foaming occurred during the test, proving the necessity of silane modification of antibacterial agents to improve dispersibility.

Claims

1. A biodegradable bio-based polyurethane wood protective coating, characterized in that, By weight, it includes the following components: Modified bio-based polyester polyol: 40-60 parts; Crosslinking agent: 10-20 parts; Antibacterial agent: 3-8 parts; Weather resistant agent: 1-3 parts; Hydrolysis stabilizer: 2-5 parts; Solvent: 20-30 parts; Coupling agent: 1-3 parts; Leveling agent: 0.5-1.5 parts; Defoamer: 0.5-1.5 parts.

2. The biodegradable bio-based polyurethane wood protective coating according to claim 1, characterized in that: The modified bio-based polyester polyol is obtained by modifying bio-based polyester polyol prepared from renewable biomass resources, dicarboxylic acid and diol. The modification involves using at least one hydrophobic modifier selected from lauric anhydride, palmitic anhydride, glycidyl palmitate, and glycidyl stearate to hydrophobically modify the bio-based polyester polyol. The renewable biomass resources include at least one of castor oil, soybean oil, and rice husk alcohol; the dicarboxylic acid includes at least one of adipic acid, succinic acid, and sebacic acid; and the diol includes at least one of 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol.

3. The biodegradable bio-based polyurethane wood protective coating according to claim 1, characterized in that: The antibacterial agent is modified nano-zinc oxide supported porous silica, and its preparation method includes the following steps: P1: Add porous silica to an ethanol-water solution, disperse by ultrasonication, then add zinc nitrate and stir to obtain a pre-dispersion. P2: Add sodium hydroxide solution dropwise to the pre-dispersion obtained in step P1 to adjust the dispersion to alkaline and allow precipitation. After precipitation, centrifuge to collect the solid, wash and dry it to obtain the pre-dispersion powder. Then, calcine the obtained pre-dispersion powder at high temperature and cool it to obtain nano zinc oxide supported porous silica. P3: Add KH550 silane coupling agent to an ethanol-water solution, stir and sonicate to hydrolyze to obtain a hydrolysate; then add the nano-zinc oxide-supported porous silica obtained in step P2 to the hydrolysate, heat and stir to react, and after the reaction is completed, centrifuge, wash and dry to obtain modified nano-zinc oxide-supported porous silica.

4. The biodegradable bio-based polyurethane wood protective coating according to claim 3, characterized in that: In step P1, the concentration of the ethanol-water solution is 70%, and the particle size of the porous silica is 1-5 μm. In step P1, the mass ratio of ethanol-water solution to porous silica is 1:(0.06-0.12), and the mass ratio of ethanol-water solution to zinc nitrate is 1:(0.1-0.16). In step P1, ultrasonic dispersion is performed for 10-30 minutes, and stirring is performed at a speed of 200-600 rpm for 10-30 minutes. In step P2, the sodium hydroxide solution concentration is 2 mol / L, and the alkalinity is adjusted to pH 11-12. In step P2, washing is performed by sequentially washing with deionized water and ethanol, drying is performed at 80-100 ℃ for 12-24 h, and high-temperature calcination is performed by calcining in a muffle furnace at 500-600 ℃ for 4-6 h. In step P3, the concentration of the ethanol-water solution is 95%, the volume ratio of the ethanol-water solution to the KH550 silane coupling agent is 1:(0.03-0.07), and the addition ratio of nano-zinc oxide-supported porous silica is 0.05-0.2 g / ml. In step P3, the stirring and ultrasonic hydrolysis involves stirring at 200-600 rpm for 5-15 minutes and then ultrasonically hydrolyzing for 20-40 minutes to achieve complete hydrolysis. The heating and stirring reaction was carried out at 40-60 ℃ for 4-6 h. In step P3, washing involves sequentially washing with deionized water and ethanol, and drying involves drying at 80-100 ℃ for 12-24 hours.

5. The biodegradable bio-based polyurethane wood protective coating according to claim 1, characterized in that: The weather-resistant agent is at least one of graphene, graphene oxide, and silane-modified graphene oxide. The crosslinking agent is at least one of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and trimers or biuret derivatives of the above substances. The hydrolysis stabilizer is at least one of Lanxess Stabaxol I, Lanxess Stabaxol P200, Lanxess Stabaxol P100, and BASF Irganox GX-2411; The solvent is at least one of butyl acetate, propylene glycol methyl ether acetate, and dimethyl carbonate. The coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. The leveling agent is a polyether-modified polydimethylsiloxane leveling agent, and the defoamer is a polysiloxane / polyether copolymer defoamer.

6. A method for preparing a biodegradable bio-based polyurethane wood protective coating as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation and modification of bio-based polyester polyols: S11. In a reactor equipped with a water separator, condenser and stirring device, add diacid, diol and renewable biomass resources, heat and stir under an inert atmosphere to carry out esterification and dehydration reaction until a bio-based polyester polyol with the required hydroxyl value and acid value is obtained. S12. Add the bio-based polyester polyol obtained in step S11 and the hydrophobic modifier into a beaker, heat and stir to carry out alcoholysis esterification reaction, and obtain modified bio-based polyester polyol. S2. The modified bio-based polyester polyol obtained in step S1 is mixed with solvent, antibacterial agent, weather resistant agent, hydrolysis stabilizer and coupling agent, and dispersed at high speed to obtain premixed slurry; S3. Add crosslinking agent, leveling agent and defoamer to the premixed slurry obtained in step S2, disperse and mix evenly to obtain the biodegradable bio-based polyurethane wood protective coating.

7. The method for preparing a biodegradable bio-based polyurethane wood protective coating according to claim 6, characterized in that: The mass ratio of the dicarboxylic acid, diol, and renewable biomass resources mentioned in S11 is 1:(0.3-0.6):(0.1-0.5). The esterification and dehydration reaction described in S11, which involves heating and stirring under an inert atmosphere, is carried out under a nitrogen atmosphere by slowly heating to 180-220℃ at a rate of 2-3℃ / min for 4-6 hours. The hydroxyl value described in S11 is 50-200 mg KOH / g, and the acid value is less than 5 mg KOH / g; The mass ratio of the bio-based polyester polyol to the hydrophobic modifier described in S12 is 1:(0.08-0.12). The alcoholysis esterification reaction described in S12 is carried out at 120-140 °C for 2-3 h.

8. The method for preparing a biodegradable bio-based polyurethane wood protective coating according to claim 6, characterized in that: The high-speed dispersion described in S2 refers to dispersion for 30-45 minutes at a rotation speed of 1000-1500 rpm; The uniform dispersion and mixing described in S3 refers to dispersion for 10-15 minutes at a rotation speed of 500-800 rpm.

9. An application of a biodegradable bio-based polyurethane as described in any one of claims 1-5 to wood protection.

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